This invention relates generally to traffic control systems and, more particularly, to traffic control systems for controlling multiple intersections.
The flow of traffic along city streets is greatly improved if the traffic signals at related intersections are coordinated. Numerous attempts have been made to coordinate traffic controls at related intersections, but most of these systems rely on interconnecting traffic controllers at the related intersection using hard wire connections. The use of hard wire connection is expensive and environmentally disruptive to construct.
Recently, attempts have been made to coordinate traffic controls at related intersections without the use of hardwire connections. These methods rely on the precise timing of the individual traffic signals using controllers with highly accurate clocks. Each controller controls the traffic signals at an individual intersection based upon a set of detailed control tables. The control tables are prepared from traffic data studies which are periodically conducted at the several intersections.
Unfortunately, such methods which avoid the use of hardwire connections have not been wholly successful. This is because the control tables rapidly become outdated. Traffic control studies are considered awkward, time-consuming and expensive and are therefore infrequently conducted. Thus, the traffic control tables are infrequently, if ever, updated.
Accordingly, there is a need for an improved traffic control method which avoids the aforementioned problems in the prior art.
The invention satisfies this need. The invention is a method for controlling a plurality of traffic intersections wherein each traffic intersection is defined by the intersection of at least two streets. Each traffic intersection has an alternating traffic control signal for controlling the flow of traffic through the intersection. Also, each traffic intersection has at least one traffic flow sensor for sensing the flow of traffic on at least one of the two streets and for generating traffic flow data derived therefrom. Each traffic intersection also has a clock for measuring time and for generating time data related thereto. Finally, each traffic intersection has a traffic signal controller for controlling the traffic control signal pursuant to a set of one or more operating parameters. The method of the invention comprises the steps of (a) continuously storing the traffic flow data and the time data in a data storage unit, (b) downloading the traffic flow data and the time data from the data storage device to a computer, (c) using a computer to generate a new set of operating parameters for each of the traffic controllers, the new set of operating parameters being derived from the traffic flow data and from the time data, (d) installing the new set of operating parameters into each of the traffic controllers, (e) controlling the plurality of traffic intersections with the traffic controllers after the new sets of operating parameters have been installed in the traffic controllers in step (d), and (f) repeating steps (b)-(e) at least as often as every 180 days.